Voltage multiplication apparatus



April 12, 1966 M. R. CLELAND VOLTAGE MULTIPLICATION APPARATUS '7Sheets-Sheet 1 Filed March 5, 1962 NEQ T April 12, 1966 M. R. CLELANDVOLTAGE MULTIPLICATION APPARATUS '7 Sheets-Sheet 2 Filed March 5, 1962April 12, 1966 M. R. CLELAND VOLTAGE MULTIPLICATION APPARATUS 7Sheets-Sheet 3 Filed March 5, 1962 CSY/ csxa

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VOLTAGE MULTIPLICATION APPARATUS Filed March 5, 1962 7 Sheets-Sheet 6can c5242 55x3 0x1\ fi RNA 7 Rwz RAB 9 RNB 0)! IV I 023 J jicszz c523April 12, 1966 M. R. CLELAND 3,246,230

VOLTAGE MULTIPLICATION APPARATUS Filed March 5, 1962 7 Sheets-Sheet 7United States Patent 3 246,230 VOLTAGE MULTIILICATION APPARATU MarshallR. Cleland, Huntington Station, N.Y., assignor to Radiation Dynamics,line, Westbury, N.Y., a corporation of New York Filed Mar. 5, 1962, Ser.No. 177,660 18 Claims. (Cl. 321-) This invention relates to voltagemultiplication apparatus, and more particularly to voltagemultiplication apparatus which provides a high voltage DC. outputpotential.

Among the several objects of this invention may be noted the provisionof voltage multiplication apparatus which operates with increasedefficiency to convert relatively low voltage A.C. power to a highvoltage DC. output potential at improved DC. output current levels andreduced voltage ripple; the provision of such apparatus which is compactand has reduced insulation requirements; the provision of apparatus ofthe class described which has decreased cooling requirements and canutilize polyphase A.C. power sources which'operate at relatively lowfrequencies; the provision of voltage multiplication apparatus which mayemploy an A.C. power source of lower potential and has reduced powerdissipation; the provision of apparatus of the class described whichmore efficiently utilizes rectifier-s of decreased ratings; theprovision of such apparatus which may conveniently incorporate anaccelerator tube for the production of high energy ion or electronbeams;

3,246,230 Patented Apr. 12, 1966 1 units are energized or driven from asingle relatively low or the inductor itself may be part of the tankcircuit of an and the provision of voltage multiplication apparatuswhich is reliable in operation and economical in cost. Other objects andfeatures will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the constructions hereinafterdescribed, the scope of the invention being indicated in the followingclaims.

In the accompanying drawings, in which several of various possibleembodiments of the invention are illus trated,

FIG. 1 is an exploded side oblique view, partially diagrammatic, of aportion of one embodiment of voltage multiplication apparatus of myinvention;

FIG. 2 is a cross section taken on line 22 of FIG. 1;

FIG. 3 is a schematic circuit diagram illustrating certain principles ofthe present invention;

FIGS. 4 and 5 are views respectively similar to those of FIGS, 1 and 2,but of a second embodiment of my invention;

FIGS. 6 and 7 are views respectively similar to those of FIGS. 1 and 2of another embodiment of this invention but with the grounded containerand the intermediate electrodes omitted in FIG. 6; and

FIGS. 8 and 9 are views respectively similar to those of FIGS. 1 and 2of still another embodiment of my invention, but with the groundedcontainer and intermediate electrodes omitted in FIG. 8.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

Several types of apparatus are now utilized in generating high voltageD.C. potentials in the order of a million and more volts. One of thesetypes of apparatus, which is particularly advantageous in suplying thesehigh D.C. voltages, especially at relatively high current levels in theorder or 1 to 10 or more milliamperes, is the cascaded rectifier, suchas is disclosed in my coassigned US. Patent 2,875,394. In this type ofvoltage multiplication apparatus, a number of rectifier units areserially connected so that the sum of their respective DC. outputpotentials is supplied at high voltage D.C. terminals, and all rectifierR.-F. oscillator or amplifier, the capacitance of the shell electrodesand associated components providing at least a portion of thecapacitance parameter of an LC circuit resonant at the frequency of theA.C. power source. One of the difiiculties encountered with voltagemultiplication apparatus of this and many other types is the minimizingof power losses .and generally increasing the efiiciency of operation.

In accordance with the present invention, voltage multiplicationapparatus is provided which greatly improves the operational efiiciency,minimizes power losses, permits the use of lower voltage A.C. powersources and more compact structural dimensions, as well as markedlyreducing the insulation requirements. In essence my invention comprisesa plurality of rectifying modules, each having a rectifier connectedbetween a positive and a negative terminal. These module terminals areseries-connected between a pair of high-voltage D.C. terminals, and eachmodule further includes at least two corona shields with an inductorconnected therebetween. A source of A.C. power is connected to at leasttwo metallic electrodes to establish an A.C. electric fieldtherebetween. The corona shields and the rectifying modules arepositioned in this A.C, field so that electrical energy is capacitivelycoupled to said corona shields to establish substantially equal A.C.potentials across each of the inductors and each inductor is connectedto energize its respective rectifier unit. Preferably, each of therectifying modules constitutes a portion of a series LC circuitincluding the interelectrode capacitances between the metallicelectrodes and the respective corona shields. By maintaining thefrequency of the A.C. power source at approximately the natural resonantfrequency of these LC circuits, the magnitude of the A.C. voltagedeveloped across each of the inductors will substantially exceed that ofthe A.C. power source.

' Referring now more particularly to FIGS. 1 and 2, an electricallygrounded, heavy steel, cylindric, gas-tight, pressure container isindicated at numeral 1. Enclosed within this container are a number ofidentical rectifying modules, each indicated generally by referencecharacters RMA, RMB and RMN. Each of these rectfier units includes aninductor, such as indicated at IA, 1B and IN,

, respectively connected between two pairs of commonly connected arcuatemetallic corona shields CSAl, CSA2; CSBl, CSBZ; CSCI, CSCZ; CSMI, CSM2;and CSNI, CSN2. It will be understood that single or common coronashields may be used instead of pairs of shields. Reference charactersCXA, CXB, and CXN indicate the interelectrode capacitances between theopposed pairs of corona shields. Each of these rectifying modules RMA,RMB and RMN further includes a rectifier, such as a diode, DA, DB and DNconnected in shunt with its respective inductor IAIN and theinterelectrode capacitances CXA-CXN. As each pair of corona shieldsCSAl, CSALCSNI, CSN2 is respectively commonly connected to oppositeelectrodes of the rectifier units DA-DN, successive pairs of coronashields constitute opposite polarity terminals of the respectiverectifying modules. For example, the negative terminal of rectifyingmodule RMA is CSAI, CSA2, while the positive terminal thereof is CSB'l,CSB2. As the CSBI, CSB2 shields constitute the negative terminal of therectifying module RMB and C801, CSC2 are the positive terminal thereof,these terminals of the rectifying modules are seen to be connected inseries or cascade between a pair of high voltage D.C. terminals HVl andHVZ. The latter terminal is electrically connected to the groundedcontainer 1, while the former high voltage terminal HVl is electricallyconnected to a dome-shaped metallic electrode HVD. Preferably R.-F.chokes RFC are series-connected in the high voltage D.C. circuit toinhibit the flow of RF. in any electrical load to be energized byconnection to terminals HVl and HV2. A DC. blocking capacitor, asindicated at CA, CB and CN, is also included in each of the rectifyingmodules RMA-RMN of this embodiment of FIGS. 1 and 2, each of which isserially connected with the respective module inductor IAIN. The A.C.impedance of each of these capacitors CA, CB-CN is much lower than thatof the respective inductors IA, IB-IN so that their parameters can beignored in the A.C. analysis.

The assembly of the cascaded rectifying modules is positioned between apair of spaced-apart metallic shell electrodes E1 and E2. The electrodesare connected to a source of A.C. power, such as for example an R.-F.oscillator or power amplifier capable of supplying potential of about10,000 volts or more at a frequency range in the order of 20 to 200 kc.to electrodes E1 and E2. The electric field thus established betweenelectrodes E1 and E2 is utilized to drive or energize the rectifyingmodules RMA-RMN by applying substantially the same A.C. potential acrossopposed pairs of corona shields CSAl, CSA2; CSB1, CSBZ; CSCl, CSCZ;etc., via respective interelectrode capacitances CESA, CESB, CESC, CESM,and CESN. Thus A.C. power is coupled capacitively from electrode E2 tocorona shields CSAl, CSA2 via the capacitance CESA therebetween.Similarly A.C. power is coupled capacitively from electrode Ell viainterelectrode capacitance CESB to CSBI, CSB2. The capacitances betweenthe electrodes E1 and E2 and the grounded container 1 are indicated atCEGl and CEG2. It will be noted that the corona shields and the shellelectrodes are arranged symmetrically along the longitudinal axis ofcontainer 1, thus permitting the mounting along the central axis of anelongate accelerator tube AT (shown only in FIG. 2 so as to avoidobscuring circuit details in FIG. 1) across which the high voltage DC.potential produced by the voltage multiplication apparatus of thisinvention may be applied. Tube AT constitutes an exemplary load adaptedto be connected across the high voltage terminals HVI and HV2.

The circuit of FIGS. 1 and 2 is shown schematically in FIG. 3, togetherwith an exemplary source of A.C. or R.-F. power constituted by a pair oftriode vacuum tubes VM and VTZ connected in a push-pull amplifiercircuit and excited by a generator GN, which may be any conventionalR.-F. signal generator, such as an oscillator. The usual D.C. platevoltage for the anode-cathode circuits of VTl and VT2 is suppliedthrough the R.-F. chokes RFCI and RFC2, as indicated at B+, the negativeteranimal of the plate voltage supply being grounded as is customary.The control grids are connected to respective terminals of generator GNthrough two similar parallel RC circuits or grid-leak networks RCA andRCB which develop grid bias so as to achieve the high tube efficiency ofclass C operation. The anodes of VT1 and VT2 are connected by conductors3 and 5 to the shelf electrodes E1, E2; these electrodes, the coronashields and rectifying modules constituting an LC tank circuit for thispush-pull power amplifier. It will be noted that although only tworectifying modules RMA and RMB are illustrated with their associatedcorona shields in FIG. 3, the others are all effectively connected inparallel therewith relative to the A.C. drive as described above.

Operation of the apparatus of this embodiment is as follows: Assumingthat the output A.C. potential impressed across El, E2 via conductors 3and 5 is 10,000 volts, A.C. power is coupled to RMA-RMN via theinterelectrode capacitances CESACESN. For maximum effectiveness inproducing the maximum DC. potential at HVl, HV2, the maximum A.C.voltage should be applied across each rectifying module. This isaccomplished in accordance with the present invention inasmuch as eachrectifying module constitutes a portion of a series LC circuit whichincludes the inductance of the inductor, such as IA, and the twointerelectrode capacitances CESA, CESB. The interelectrode capacitanceCXA between the opposed pairs of corona shields CSAl, CSA2 and CSBl,CSB2 and the inherent capacitance between the electrodes of therectifying unit DA are efiTectively in parallel with the inductor IA.The inductive and capacitive parameters of these circuit components andthe frequency of the A.C. power source are chosen so that the laterapproximates the resonant frequency of these series LC circuits, eachincluding a rectifying module and its respective associatedcapacitances. As the capacitors CA, CB-CN function simply to block D.C.they will have a very low impedance at the frequency of operation ofthis voltage multiplication apparatus.

By applying an A.C. voltage of, say, 10,000 volts across electrodes E1and E2 by means of the power amplifier including VTl and VT2, a voltageof 50,000 volts or more is developed across each of the inductors IA,IBIN. This amount of voltage gain between the applied across E1, E2 andthat developed across IA, IB-IN is a function of the Q of the seriesresonant LC circuits described above. If there is an effective Q of 5,for example, under usual circuit loading conditions, there will be avoltage developed across each of the inductors of the respectiverectifying modules that is five times that of the voltage applied acrossE1 and E2. Similarly, with an applied voltage of 10 kv. across E1 and E2and a Q of 10, a voltage of about kv. will be developed across each ofthe inductors.

It will be noted that although a push-pull configuration vacuum tubepower amplifier is illustrated as a source of A.C. power, otherequivalent power sources such as semiconductor transducer units andmechanical generators may be employed. Also, as described andillustrated in my coassigned copending application Serial No. 49,773,field August 15, 1960, the source of A.C. power may be a self-excitedsingle-ended or push pull oscillator in which instance the grids, orequivalent electrodes of transistor or semiconductor transducers, areexcited by a signal or signals fed back in proper phase relationship (bymeans of probes, etc., such as shown in the aforesaid patentapplication, but preferably positioned adjacent respective coronashields, e.g., CSMI, and CSNl, rather than electrodes E1 and E2 inasmuchas the R.-F. potential across any opposed set of corona shields isgreater than across E1, E2). Further, it will be understood that insteadof utilizing the L and C of the assembly of the electrodes E1 and E2 andthe rectifying modules as the tank circuit of the amplifier oroscillator, this assembly can be driven or excited from a separate tankcircuit or other A.C. generator. It is preferred that the A.C. powersource be a relatively low impedance source. The capacitances CEGl andCEG2 can be conveniently adjusted by varying the spacing between thegrounded container 1 and the electrodes E1, E2 to adjust the impedancematching, or additional separate capacitors could be utilized betweenground and the anodes of VTl and VT2 for this purpose.

As the voltage differential between the grounded container andelectrodes E1, E2 is quite low, the spacing between these elements maybe small and the insulation requirement-s reduced. Also, as circulationof extremely high R.-F. currents and power losses are minimized, theheat generated by the voltage multiplication apparatus of my inventionis lessened and this simplifies the design and construction of thisapparatus, and decreases the cost of cooling accessories, etc. Thus, aphysically quite compact generator with a minimum of expensive coolingequipment can be constructed that'will develop extremely highvoltageseg', on the order of 5 or 6 mv. or higher, at substantial current levelsin the order of several milliamperes and more. 1

The second embodiment of voltage multiplication apparatus of thisinvention is illustrated in FIGS. 4 and 5 and is quite similar to thatof FIGS. 1 and 2. The principal difference between the two embodimentsis that a full-wave recti-fier'configuration is utilizedin eachrectifying module (RMAl and RMNI in FIGS. 4 and 5), rather than thehalf-wave rectifier arrangment employed in FIGS. 1 and 2. Thus in FIGS.4 and 5 an exemplary rectifying module RMAI includes inductor IAconnected between the two pairs of corona shields CSAI, CSA2 and CSBl,CSBZ, the former spaced adjacent metallic electrode E2 while the latteris positioned close to electrode E1. The full-wave rectifier includesrectifying units DAL DA2, DA3 and DA4 connected in a bridgeconfiguration with the input junctions connected across IA and'theoutput junctions constituting the terminals of the rectifying modules asindicated at 7 and 9. Another identical rectifying module RMNI,analogously referenced, is also shown in FIG. 4 having its outputterminals 10 and 12 serially connected in the D.C. high voltage circuit.

The operation of the voltage multiplication apparatus of this embodimentis essentially the same as that de: scribed above in regard to FIGS. 1and 2 'with only minor differences. For example, as the full-waverectification reduces the ripple; amplitude of the rectified D.C.,the,.R. F. chokesR-FC of FIG. 1 are not needed in this embodiment. TheD.C. blocking capacitors CA, CB and CN are also unnecessary in thisembodiment and accordingly are omitted, Also, as indicated above, thecorona shields are not utilized as the terminals. of the rectifyingmodules in this .second embodiment, although these coronatshieldsjn:both embodiments do serve the dual functions of providing coronaprotection as well as constituting 'one' electrode 'of the capacitancewhich serves to couple A.C. power from-the shells'El and E2 totherectifying modules. V,

"Thethird embodiment of this invention, illustrated in FIGS hfand .7, isagain quite similarto those described above, One essential 'andimportantdistinction is that 'a three-phase A.C. power sourceis utilized todrivejor energize three symmetrically disposed metallic electrodes E3,E4 and E5,"eacl1" connected to one phase of. the threephase powersupply. Positioned adjacent and respectively; equidistantly spaced fromthese three electrodes are sets of three arcuate coron'a'shields CSXl,CSYl, CSZl; CSXZ, CSY2, CSZ2; and CSX3, CSY3, CSZ3. These sets, of.three corona rings, three inductors IX, IY and IZ, and, sixrectifierunits'DXI, DXZ, DY1, DY2, and DZ1 and DZZ comprise anindividaul rectifying module of this embodiment, there being any desirednumber of such modules aligned along the longitudinal axis of tank landconcentrically relative to the axis accelerator tube 'AT. The terminalsof, each of these rectifying modules are serially connected to provide ahigh D.C. potential (which is thesum of eachof the rectified outputpotentialsof each of the modules) at the D.C. high voltage terminals ofthe voltage multiplication.apparatus. r The inductors, IX, -IY and IZare commonly connected at 'a metallic ring RN2, the other terminals ofthese three inductors being respectively connected to corona shields.CSXZ, CSY2 and C822. The three rectifier units DXl, DY1 and DZ1 arerespectively interconnected between corona shields CSXl, CSYl and C521and a common connection to another concentric metallic ring RN1.Identical interconnections are made between CSX3, CSY3 and CSZ3 with theremaining three rectifier units DX3, DY3 and DZ3 and between theserectifier units and a third ring RN3. I It will be noted that each ofthe two sets of three rectifiers (DX 1 DY 1, DZl and DX3, DY3, DZ3) andthe three inductors (IX, IY, IZ)

6 are each interconnected in a Y configuration. The three corona shieldsCSX1, CSX2 and CSX3 are commonly electrically connected and could beconstituted by a single arcuate section if desired. Shields CSYI', CSY2and CSY3, as well as CSZI, CSZ2 and CSZ3, are respectively similarlyelectrically commonly interconnected. Ring RN1 constitutes the negativeterminal of this exemplary rectifying module, while ring RN3 constitutesthe positive polarity terminal thereof. Ring RN1 is connected by a wire7 to a similar ring RNA which is the positive terminal' of an identicalrectifying module to the left of the one illustrated. Ring RN3 islikewise connected by a conductor 9 to an identical ring RNB which isthe negative terminal of an identical rectifying module to the right ofthe one illustrated.

It is preferred that the inductors 1X, IY and IZ be of the solenoidaltype with their axes radially positioned relativeto the centrallongitudinal axes of the rectifying modules so as to be parallel to theR.-'F. electric field established between the arcuate corona shields andthe central ring RN2 which thereby insures uniform voltage distributionalong the full length of the inductors and rectifiers. The use of therings RN1, RN2 and RN3 is optional but preferred inasmuch as they serveto prevent R.-F. heating of resistor strings RS interconnected betweengrading rings of accelerator tube AT. These rings RN1, RN2, RN3 are alsoespecially useful in the three phase embodiment, inasmuch as it providessome capacitive loading of the junction points of the floating bridgecircuits.

The operation of the embodiment of FIGS. 6 and 7 is again similar tothat described above, except that the rectification of out-of-phasevoltages developed across IX, IY and IZ is accomplished by a three-phasebridge. Again the A.C. potentials developed across these inductors issubstantially greaterthan that applied to' elec-' trodes E1, E2 and E3because of the series LC circuit relationship described above. The useof a three-phase configuration, as illustrated in this embodiment and inthe succeeding one, provides a more eificient use of rectifiers whereinsmaller rating rectifiers maybe utilized and also permits operation-atlower frequencies of the A.C. power supply.

Still \another embodiment of my invention is illustrated in FIGS. 8 and9. As in the preceeding embodiment, a three-phase A.C. power source isemployed to drive the three elongate, arcuate-in-crosseection, metallicelectrodes E3, E4 and E5. A typical three-phase A.C. power supply isindicated generally at ACP interconnected by leads 11, 13 and 15 tothese three electrodes. The only significant differences between thisand the preceding embodiment are the delta configuration of the threeinterconnected inductors IXY, IXZ and IYZ, and the elimination of theinner shielding rings RN1, RN2, and RN3. The Y-connected rectifiers DX1,DY1 and DZ1 have a common junction as indicated at 17, While theY-connected rectifiers DX3, DY3 and DZ3-ha1ve a common junction at 19,which junctions 17 and 19 respectively constitute the negative andpositive terminals of this exemplary rectifying module. These terminalsof this one module are serially connected to the terminals of adjacentidentical rectifying modules.

The illustrative three-phase power source ACP includes any customaryA.C. or R.F. generator GN1 having two phase-shifter networks PS1 and PS2(to effect a-+l20 and a 12() phase shift relative to the time base ofthe drive signal present on conductor 17) respectively interconnected tothe control grids of vacuum tubes VTS and VT3. Conductor 17 is connectedto the grid of a third amplifier tube VT4, the cathodes of thesethreetubes being connected via resistors R1, R2 and R3 to ground, and bymeans of wires 19, 21 and 23, and the usual grid-leak networks GL1, GL2and GL3, t the control grids of a three-phase power amplifier stage in-7 cluding vacuum tubes VT6, VT7 and VT8. The anodes of VT3-VT5 arecommonly connected to the positive terminals of a DC. plate supply, thenegative terminal of which is grounded. These three tubes VTS-VTS andtheir associated components constitute a cathode-follower driver for thefinal stage amplifier VTd-VTS, the cathodes of which are commonlygrounded. The anodes of these tubes VT6, VT7 and VT8 are interconnectedby DC. blocking capacitors C1, C2 and C3 to conductors 11, 13 and tosupply excitation power to the driving electrodes E3, E4 and E5. Theanodes of VT6-VT8 are connected by means of three additional R.F. chokesRFC6-R'FC8t0 a DC. plate voltage supply, the negative terminal of whichis grounded. Three high impedance isolation chokes RFC9-RFC11 areconnected from conductors 11, 13 and 15 respectively to ground toprevent buildup of DC. potentials on these conductors due to occasionalelectrical discharges from the corona shields.

The operation of this FIGS. 8 and 9 embodiment is similar to thatdescribed above with regard to the other three-phase voltagemultiplication apparatus.

It will be understood that although half-, fulland three-phaseconfiguration rectifying modules and apparatus have been specificallydisclosed, other polyph-ase rectifier configurations may be utilized, ifdesired. Also, it will be noted that any of the conventional types ofrectifiers (e.g., vacuum, gas, semiconductor, dry type, etc.) may beused and that several units thereof may be interconnected to consti-mtea rectifier unit of this invention. Further, these rectifiers may bereversed in their sockets or interconnection to reverse the polarity ofthe high voltage D.C. terminals, if desired. Any voltage regulatorcircuitry may also be utilized in conjunction with the A.C. powersources employed to further enhance the voltage versus load curve orcharacteristics of this apparatus.

In view of the above, itwil-l be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

What is claimed is: v

1. Voltage multiplication apparatus comprising a plurality of rectifyingmodules each having a rectifier unit connected between a positive and anegative terminal, the terminals of said modules being series-connectedbetween a pair of high voltage D.C. terminals, each module furtherincluding at least two corona shields with an inductor connectedthere'between, at least two metallic electrodes, a source of A.C. powerconnected to said electrodes to establish an A.C. electric fieldtherebetween, said corona shields being positioned in said A.C. fieldwhereby electrical energy is capacitively coupled to said corona shieldsto establish substantially equal A.C. potentials across each of saidinductors and each inductor is connected to energize its respectiverectifier unit.

2. Voltage multiplication apparatus as set forth in claim 1 in whicheach of the rectifying modules constitutes a portion-of a series LCcircuit including the interelectrode capacitan-ces between themetallicelectrodes and the respective corona shields and the frequency of -saidA.C. power source approximates the natural resonant frequency of said LCcircuits, whereby the magnitude of the A.C. voltage developed acrosseach of said inductors substantially exceeds that of the A.C. powersource. 1

3. Voltage multiplication apparatus as set forth in claim 1 in whicheach of said rectifier units comprises a halfwave rectifier, andeachf'of'said inductors is respectively parallel-connectedtherewith...

4. Voltage multiplication apparatus as set forth in claim-Sin which eachrectifying module further includes 8 a'D.C. blocking capacitorinterconnected in a loop circuit between the inductor and the rectifierunit.

5. Voltage multiplication apparatus as set forth in claim 1 in whicheach of said rectifying units is a fullwave rectifier. I

6. Voltage multiplication as set forth in claim 5 in which each of saidfull wave rectifiers is connected in a bridge rectifier configurationhaving input terminals and output terminals, said inductor beingconnected across said bridge input terminals and said bridge outputtermi-j nals constitute said positive and negative terminals of saidmodule. i v

7. Voltage multiplication apparatus as set forth in claim 1 in whichsaid A.C. power source is a three phase A.C. power source and there arethree metallic electrodes, one connected to each of said" phases, and atleast three corona shields, each module including. three inductors andtwo sets of three rectifier units.

8. Voltage multiplication apparatus as set forth in claim 7 in whicheach of said sets of three rectifier units is Y-connected. I

9. Voltage multiplication apparatus as set forth in claim 8 in whichsaid three inductor s are Y-connected.

10. Voltage multiplication apparatus as set forth in claim 8 in whichsaid three inductors are delta-connected.

11. Voltage multiplication apparatus comprising at least two opposedmetallic shells having-their respective Edges spaced apart, a pluralityof rectifying modules each having a rectifier unit connected between apositive and a negative terminal, the terminals of said modules beingseries-connected between a pair of high voltage D.C, terminals, saidmodules being generally symmetrically positioned within the spaceenclosed by said metallic shells and about a central longitudinal axisof said opposed metallic shells, each module further including at leasttwo corona shields with an inductor connected therebetween, saidcoronashields of each module being positioned in a plane generally transverseto said longi tudinal axis, and a source of AC. power connected to saidmetallic shells to establish a radial A.C. electric field therebetweentransverse to said axis whereby electrical energy is capacitivelycoupled to said corona shields to establish substantially equal A.C.potentials across each of said inductors and each inductor is connectedto energize its respective rectifier unit.

12. Voltage multiplication apparatus asset forth in claim 11 in whicheach of therectifying modules consti tutes a portion of a series LCcircuit including them.- terelectrode capacitances between themetallicelectrodes and the respective corona shields and the frequency of saidA.C. power source approximates the natural resonant frequency of said LCcircuits, whereby the magnitude o f'the A.C. voltage developed acrosseach ofsaid inductors'substantially exceeds that of the A.C.p'owersourcje,

13. Voltage multiplication apparatus as set forth in claim 11 in whicheach of said inductors is a solenoidal coil having its longitudinal axisaligned radially relative to the axis of said metallic shells. I

14. Voltage multiplication apparatus as set forth in claimjll in whichsaid positive and negative terminals comprise a plurality of parallelspaced apart metallic rings concentrically aligned along saidlongitudinal axis.

15. Voltage multiplication apparatusas set forth in claim 14 in whichsaid A.C. power sources is a three phase A.C. power source and there arethree metallic shells symmetrically positioned about said longitudinalaxis, one connected to each of said phases, and at least three corona.shields, each module including three inductors and two setsof threerectifier units.

16. Voltage multiplication apparatus as set forth in claim 15 in whicheach of said sets of three rectifier units is Y-connected.

17. Voltage multiplication apparatus as set forth in claim 15 in whichsaid three inductors in each module are Y-connected, and the commoninter-connection thereof comprises a metallic ring concentricallyaligned along said longitudinal axis.

18. Voltage multiplication apparatus as set forth in claim 16 in whichsaid three rectifying units are Y- 5 connected and the commoninterconnection thereof comprises a metallic ring concentrically alignedalong said longitudinal axis.

10 References Cited by the Examiner UNITED STATES PATENTS 2,214,8719/1940 Westendorp 321-15 2,875,394 2/1959 Cleland 321-15 MILTON O.HIRSHFIELD, Primary Examiner. LLOYD MCCOLLUM, Examiner.

1. VOLTAGE MULTIPLICATION APPARATUS COMPRISING A PLURALITY OF RECTIFYINGMODULES EACH HAVING A RECTIFIER UNIT CONNECTED BETWEEN A POSITIVE AND ANEGATIVE TERMINAL, THE TERMINALS OF SAID MODULES BEING SERIES-CONNECTEDBETWEEN A PAIF OF HIGH VOLTAGE D.C. TERMINALS, EACH MODULE FURTHERINCLUDING AT LEAST TWO CORONA SHIELDS WITH AN INDUCTOR CONNECTEDTHEREBETWEEN, AT LEAST TWO METALLIC ELECTRODES, A SOURCE OF A.C. POWERCONNECTED TO SAID ELECTRODES TO ESTABLISH AN A.C. ELECTRIC FIELDTHEREBETWEEN, SAID CORONA SHIELD BEING POSITIONED IN SAID A.C. FIELDWHEREBY ELECTRICAL ENERGY IS CAPACITIVELY COUPLED TO SAID CORONA SHIELDSTO ESTABLISH SUBSTANTIALLY EQUAL A.C. POTENTIALS ACROSS EACH OF SAIDINDUCTORS AND EACH INDUCTOR IS CONNECTED TO ENERGIZE ITS RESPECTIVERECTIFIER UNIT.